<template>
  <div class="spec-preview">
    <img :src="curImgUrl"/>
    <div class="event" @mousemove="Handler"></div>
    <div class="big">
      <img :src="curImgUrl" ref="img"/>
    </div>
    <!--遮罩层-->
    <div class="mask" ref="mask"></div>
  </div>
</template>

<script>

export default {
  // eslint-disable-next-line vue/multi-word-component-names
  name: "Zoom",
  props: ['skuImageList'],
  data() {
    return {
      cursIndex: 0
    }
  },
  mounted() {
    // 点击轮播图改变大图显示图片
    this.$bus.$on('changeImgUrl', (index) => {
      this.cursIndex = index
    })
  },
  methods: {
    // 放大镜随鼠标移动
    Handler(e) {
      // 获取蒙板的dom
      const mask = this.$refs.mask
      // 放大效果的dom
      const big = this.$refs.img
      // 计算蒙板随鼠标移动之后的left和top
      let left = e.offsetX - mask.offsetWidth / 2
      let top = e.offsetY - mask.offsetHeight / 2
      // 约束范围
      if (left <= 0) left = 0 // 约束左边界
      if (left >= mask.offsetWidth) left = mask.offsetWidth// 约束右边界
      if (top <= 0) top = 0;
      if (top >= mask.offsetHeight) top = mask.offsetHeight
      // 重新设置蒙板的left和top
      mask.style.left = left + 'px'
      mask.style.top = top + 'px'
      // -2倍关系
      big.style.left = -2 * left + 'px'
      big.style.top = -2 * top + 'px'
    }
  },
  computed: {
    // 计算属性：当参与计算的data配置项中的数据发生变化时，计算属性就会计算。即计算属性也是一个响应式的数据
    curImgUrl() {
      return this.skuImageList[this.cursIndex].imgUrl || {imgUrl: ''}
    }
  }
}
</script>

<style lang="less">
.spec-preview {
  position: relative;
  width: 400px;
  height: 400px;
  border: 1px solid #ccc;

  img {
    width: 100%;
    height: 100%;
  }

  .event {
    width: 100%;
    height: 100%;
    position: absolute;
    top: 0;
    left: 0;
    z-index: 998;
  }

  .mask {
    width: 50%;
    height: 50%;
    background-color: rgba(0, 255, 0, 0.3);
    position: absolute;
    left: 0;
    top: 0;
    display: none;
  }

  .big {
    width: 100%;
    height: 100%;
    position: absolute;
    top: -1px;
    left: 100%;
    border: 1px solid #aaa;
    overflow: hidden;
    z-index: 998;
    display: none;
    background: white;

    img {
      width: 200%;
      max-width: 200%;
      height: 200%;
      position: absolute;
      left: 0;
      top: 0;
    }
  }

  .event:hover ~ .mask,
  .event:hover ~ .big {
    display: block;
  }
}
</style>